1. Field of the Invention
The present invention relates to a detector provided with plural input means for obtaining output by changes in resistance values, and more particularly to a detector that switches outputs from the plural input means with a simple circuit construction.
2. Description of the Prior Art
Some recent game controllers have, in addition to ON-OFF switches, switches that provide outputs changing in an analog fashion according to changes in push pressure. By using this type of controller in, for example, a car race game, game operations such as car speed adjustment can be performed with adjustment of the pushing force onto a pushbutton.
Input means capable of changing output by changing the push pressure are, for example, those that are provided with resistance members on a substrate thereof and have elastically deformable contacts facing the resistance members, wherein the contacts are made of a material having a lower resistivity than the resistance members. Pushing a pushbutton to press the contact against the resistance member causes resistance values to change corresponding to changes in a contact area between the contact and the resistance member.
The input means generally reduce influence of output fluctuations due to changes in environment temperature, and resistance value variations at manufacturing time by connecting an element for changing resistance values and a fixed resistor in series using the contact and delivering a potential at a midpoint between them as an output value.
FIGS. 6 and 7 show circuit configurations for a conventional detector provided with plural input means.
Input means 1a, 1b, 1c, . . . , and 1n have variable resistors VR1, VR2, VR3, . . . , and VRn individually connected in series with fixed resistors R1, R2, R3, and Rn, wherein the variable resistors VR1, VR2, VR3, and VRn each comprise the resistance member and the contact. A common source voltage Vcc is applied to the ends of the fixed resistors R1, R2, R3, . . . , and Rn of the input means 1a, 1b, 1c, . . . , and 1n, and the ends of the variable resistors VR1, VR2, VR3, . . . , and VRn are grounded together. Each input means has an output part P1, P2, P3, . . . , or Pn at a midpoint between the variable resistor and the fixed resistor, and an output from the output part is converted into a digital value by an A/D converter 2 before being presented to the CPU.
In the detector shown in FIG. 7, signals obtained from the output parts P1, P2, P3, . . . , and Pn at the midpoints are switched in order by a switching means 3 comprised of active elements before being presented to the A/D converter and the CPU.
As shown in FIG. 6, in the detector in which all the output parts P1, P2, P3, . . . , and Pn of the input means 1a, 1b, 1c, 1d, . . . , and In are converted by the A/D converter 2 before being presented to the CPU, each of the output parts P1, P2, P3, and Pn must be subjected to A/D conversion in parallel. Accordingly, the A/D converter 2 must be expansive so that plural input signals can be subjected to A/D conversion in parallel, and the CPU is also heavily loaded for data processing because plural outputs having been subjected to A/D conversion are inputted at the same time.
In the detector shown in FIG. 7, since outputs from the output parts P1, P2, P3, . . . , and Pn are switched in order by the switching means 3 comprised of active elements before being presented to the A/D converter and the CPU, an A/D converter supporting one-line outputs can be used, with the result that the circuit can be configured at a low cost, and since one-line outputs are switched and inputted to the CPU, loads on the CPU can be reduced.
However, in the detectors shown in FIGS. 6 and 7, in all of the input means 1a, 1b, 1c, . . . , and 1n, since a source voltage is applied at all times and other ends are grounded, currents keep flowing through all the input means, consuming a large amount of current.
In the detector shown in FIG. 7, since the number of channels switched by the switching means 3 must be the same as the number of the input means 1, 1b, 1c, . . . , and 1n, a switching element with a complicated structure must be used as the switching means 3. Also, the switching means 3 must switch a large number of channels and the switching of the switching means 3 is performed in multiple stages, with the result that the CPU is more heavily loaded to control the switching.
The present invention has been made to solve the above-described problems and provides a detector that, when the plural input means are provided, can reduce current consumption and lessen control loads by decreasing the number of switched channels.
A detector of the present invention is provided with plural input means each of which has an element changing in resistance value and a fixed resistor connected in series with each other, a midpoint between the element and the fixed resistor being defined as an output part, wherein one of the plural input means is held at a predetermined potential, a switching means is provided for switching in order other ends of the input means to a low potential, and an output from the output part of the input means switched to the low potential by the switching means is detected.
According to the present invention, since plural input means are placed in order into a low potential and outputs from input means placed into the low potential are detected in order, no undesired current flows through input means detecting no output, contributing to saving power consumption.
There is provided a common output path connected in common to the output parts of the plural input means, and it is desirable that an output from an input means switched to a low potential in the other end thereof is detected through the common output path.
Providing output path commons to plural input means reduces the number of output lines provided to an A/D converter and the like, and enables use of an A/D converter with fewer lines. If the common output paths are switched to provide an output to the CPU, since the number of common output paths is reduced, the number of channels to be switched can be reduced.
In the plural input means provided with the common output paths, preferably, a fixed resistor common to the individual elements of the input means is connected in series, the end of the fixed resistor is held at the predetermined potential, and the respective ends of the elements are switched to the low potential by the switching means.
By using fixed resistors common to plural elements as described above, the number of parts can be reduced.
For example, the present invention may be configured as follows: outputs from the input means are detected; a control part constituting the switching means is provided; and the control part switches in order the other ends of the input means to the low potential and switches the other ends thereof not placed into the low potential to high impedance.
In this way, switching to a low potential and output detection are carried out by a common control part (CPU) whereby a circuit configuration can be simplified. The switching means for switching to the low potential and the output detecting means may be formed in separate systems.
The elements changing in resistance value have a resistance member and a contact that has a lower resistivity than the resistance member and contacts the resistance member while deforming elastically, and resistance values of the resistance member change according to changes in a contact area between the resistance member and the contact.
The elements may have other configuration if they are those that can change in resistance value.